The present invention relates generally to an improved vacuum degassing, recycling and solvent delivery apparatus for solvents utilized in high pressure liquid chromatographic operations and/or applications, and wherein the solvent degassing, recycling and delivery apparatus is adapted for removable retention on a solvent reservoir, and wherein the system is essentially self-priming. The vacuum degassing solvent treating arrangement of the present invention is particularly designed for use in those systems wherein portions of the solvent being utilized are recycled back to the original supply reservoir and where degassing is necessary for solvent use. The solvent degassing system of the present invention further includes, as a feature, the utilization of an atmospheric impermeable composite tubing structure which is effective for isolating fluids from atmospheric contamination during transport.
The present invention is an improvement over the vacuum degassing systems disclosed in U.S. Pat. No. 5,340,384 (Sims), and that system disclosed in copending application Ser. No. 08/688,439, both of which are assigned to the same assignee as the present invention. The content of U.S. Pat. No. 5,340,384 and application Ser. No. 08/688,439 are incorporated by reference herein. While the systems disclosed in the U.S. Pat. No. 5,340,384 patent and application Ser. No. 08/688,439 function well, the present arrangement provides an advantage in terms of versatility in use and also in priming of the system.
One of the analytical chemical operations which involves the use of liquid solvents in which dissolved gases, particularly air, is detrimental and undesirable is high pressure liquid chromatography (hereinafter referred to as HPLC). In HPLC applications, the presence of small quantities of dissolved gases interferes with the accuracy and indeed the total sensitivity of the system and its operation. Furthermore, if the dissolved species is chemically reactive, such as oxygen from dissolved air, the quality of the liquid solvent is adversely affected. As the quantity of the dissolved species increases, the adverse affect likewise increases. Thus, in order to avoid these undesirable side effects, the dissolved species are typically removed by one or more degassing operations. The overall operation, particularly the HPLC operation, is rendered far more efficient when degassing can be undertaken expeditiously and without incurring additional or significant delays. Additionally, the system of the present invention utilizes a form of atmospheric impermeable composite tubing which effectively transports the liquid solvents through the system so that the solvent is isolated from potential contaminants such as the oxygen component in ambient air.
In the past, various techniques have been employed for removal of dissolved gases from HPLC solvents. These included heating of the liquid or alternatively, subjecting the solvent liquid to a reduced pressure or vacuum. Exposure of the solvent to a source of ultrasonic energy has also been employed. Degassing involving the passing of a fine stream of an inert gas such as helium or the like through the solvent has also been utilized in the past. Helium degassing and/or sparging has certain disadvantages including the selective removal of certain volatile components of mixed solvents, and furthermore requiring the presence of large vessels for the helium supply. Membrane apparatus has been successfully employed for vacuum degassing of HPLC solvents.
In certain HPLC applications, it is desirable to employ a degassing apparatus which has been thoroughly cleaned and the presence of even trace amounts of any previously employed solvent have been eliminated. In accordance with a feature of the present invention, a quick changeover vacuum degassing device has been developed which is adapted for removable retention on a solvent reservoir, particularly a bottle having a threaded opening along its bottom or base. The degassing device includes a threaded means for engaging the base threaded opening of the reservoir or bottle, with the degassing system being conveniently confined within a shrouded zone forming a vacuum chamber for housing and retaining the degassing tubing. The inlet to the reservoir is preferably arranged and disposed in the upper end of the double-ended bottle, and for purposes of accommodating flow, a vent hole may be positioned in the cap area accommodating the inlet tube. Thus, by simply engaging the threads and screwing the attachment mechanism onto the base of the bottle, the vacuum degassing and recycling apparatus of the present invention is expeditiously placed into the system for operation. Also, the apparatus of the present invention contains means for readily receiving and coupling tubing of the type typically utilized in HPLC applications, and further includes the utilization of atmospheric impermeable composite tubing which effectively isolates the solvent, particularly solvent which has been previously degassed, from exposure to atmospheric contaminants. Additionally, an integral valve structure is conveniently incorporated into the degassing mechanism.